As your read traffic increases, you might want to spread those reads across more
nodes and reduce the read pressure on any one node. In this topic, you can find how
to
add a read replica to a Redis (cluster mode disabled) cluster.

A Redis (cluster mode disabled) replication group can have a maximum of five read
replicas. If you
attempt to add a read replica to a replication group that already has five read
replicas, the operation fails.

For information about adding replicas to a Redis (cluster mode enabled) replication
group, see the
following:

Adding a Read Replica to a Replication Group (AWS CLI)

To add a read replica to a Redis (cluster mode disabled) replication group,
use the AWS CLI create-cache-cluster command,
with the parameter --replication-group-id to specify
which replication group to add the cluster (node) to.

The following example creates the cluster my-read replica and adds it
to the replication group my-replication-group. The node types, parameter
groups, security groups, maintenance window, and other settings for the read replica
are the same as for the other nodes in my-replication-group.

For more information on adding a read replica using the CLI, see create-cache-cluster in the Amazon ElastiCache Command Line Reference.

Adding a Read Replica to a
Replication Group Using the API

To add a read replica to a Redis (cluster mode disabled) replication group,
use the ElastiCache CreateCacheCluster operation,
with the parameter ReplicationGroupId to specify
which replication group to add the cluster (node) to.

The following example creates the cluster myReadReplica and adds it
to the replication group myReplicationGroup. The node types, parameter
groups, security groups, maintenance window, and other settings for the read replica
are the same as for the other nodes myReplicationGroup.